Magnetic field models
Magnetic field models for Saturn based on data obtained by the Pioneer 11, Voyager 1, and Voyager 2 spacecraft are discussed. Saturn is distinguished form earth and Jupiter by the symmetry of its internal field about its axis of rotation; however, the strong periodic modulation of Saturn's radio emission is strong evidence of some departure from axial symmetry. Analysis of energetic charged particle absorption signatures observed by Pioneer and Voyager spacecraft are consistent with axisymmetric models of Saturn's magnetic field and demonstrate that any equatorial displacement of the dipole is limited to less than 0.01 R(S). Saturn's magnetosphere appears to be intermediate in configuration to those of earth and Jupiter. An equatorial ring current of about 10 million A, confined to a 5 R(S) thick annulus with inner and outer radii of 8 and 16 R(S), has a major effect on the geometry of the outer magnetosphere. Field lines are moderately but measurably stretched out in the equatorial plane.